Polygala lutea Stipa avenacea. 



Phlox subulata. Sporobolus serotinus. 



Panicum verrucosum. 



Tephrosia Virginiana. 

 Quercus nigra. 



Itriculata subulata. 

 Phellos. 



" heterophvlla. x - • a 



1 - Xyris tiexuosa. 



" Rudkinii. 



Rubus cuneifolius. 



" Caroliniana. 

 Lycopodium inundatum. 



Solidago puberula. 



Spiranthes simplex. Catharinea crispa. 



W. W. Bailey, Pine Barren Plants in Rhode Island, Bull. Torr. 

 Bot. Club, 7, 1880, p. 98. Lists nineteen of these species which 

 were found in a limited area about Worden's Pond in southern 

 Rhode Island. 



E. W. Hervey, Flora of New Bedford and the Shores of Buzzard's 

 Bay, with a Procession of the Flowers. Notes twenty-five of these 

 plants. 



Going northward their numbers become fewer and fewer until 

 finally, as Hollick* has pointed out, some of the number originally re- 

 ported by Britton may be excluded as they are found as far north as 

 Canada ; these are Lycopodium inundatum, Asclepias obtusifolia, Juncus 

 pelocarpus, Kalmia angustifolia, Solidago puberula and Tephrosia 

 Virginiana. 



III. The Northern Flora. 



In the Cretaceous times, as already outlined, there was evidently 

 quite an extensive flora on the continent of North America ; we know 

 from the researches of Newberry and Lesquereux that in this age we find 

 the first angiosperms, so that the Cretaceous saw the dawn of the flora 

 as we know it at the present day. With the advent of the glacial 

 epoch many of the northern plants perished and the more hardy 

 northern members of the flora slowly migrated southward, some of 

 them, no doubt, living close to the margins of the ice sheet. At the 

 close of the glacial epoch, many of the plants again migrated north- 

 ward slowly and some of the distinctly southern plants moved up to 

 the area of the terminal moraine. Many adapted themselves to the 

 new soil and moved northward, but the probabilities seem to point to 

 the fact that the set of plants we have designated as pine barren 

 plants were enabled to hold their own only upon the yellow gravel, a 



*L.c, Plant distribution, etc. 



